<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>流程控制和循环语句</title>
</head>
<body>
    
</body>
<script>
    //if语句
    let month = 3;
    if(month >= 3 && month <= 5) {
        document.write("春季");
    }else if(month >= 6 && month <= 8) {
        document.write("夏季");
    }else if(month >= 9 && month <= 11) {
        document.write("秋季");
    }else if(month == 12 || month == 1 || month == 2) {
        document.write("冬季");
    }else {
        document.write("月份有误");
    }

    document.write("<br>");

    //switch语句
    switch(month){
        case 3:
        case 4:
        case 5:
            document.write("春季");
            break;
        case 6:
        case 7:
        case 8:
            document.write("夏季");
            break;
        case 9:
        case 10:
        case 11:
            document.write("秋季");
            break;
        case 12:
        case 1:
        case 2:
            document.write("冬季");
            break;
        default:
            document.write("月份有误");
            break;
    }

    document.write("<br>");

    //for循环
    for(let i = 1; i <= 5; i++) {
        document.write(i + "<br>");
    }

    //while循环
    let n = 6;
    while(n <= 10) {
        document.write(n + "<br>");
        n++;
    }
</script>
</html>